Approximately 1 in 5 Americans are infected with herpes simplex virus type 2 (HSV-2) and the approximate direct cost of genital HSV disease exceeds $200 million annually. In addition to the devastating effects of HSV infections in newborns, genital lesions caused by HSV represent a major risk factor for acquisition of HIV. The increased frequency of recurrent disease and the inability to resolve oral and anogenital HSV lesions remains a serious complication for many immunocompromised patients. There is no licensed vaccine for the prevention of HSV disease. Vaccines recently tested in clinical trial elicited high titers of specific antibody but did not protect all populations against HSV-2 infection. The proposed studies will focus on the protective responses by specific T cell subsets and examine the mechanisms by which they act in the genital epithelium, sensory ganglia, and spinal cord to resolve HSV infections. In Aim 1, we will transfer HSV-immune CD4+ and CD8+ T cell populations to bone marrow chimeric mice to examine the role of epithelial cells, innate immune cells, and IFN-gamma in clearance of HSV from the genital tract. We will determine if the cellular targets for IFN-gamma are hemopoietic or somatic cells and examine the molecular mechanisms of IFN-gamma -mediated protection of this site. HSV-1 is also emerging as an important genital pathogen. In Aim 2, we will identify the T cell subsets responsible for protection against genital HSV-1 infections. We will utilize ELISPOT and Tetramer staining to quantify recall T cell responses and assess their ability to protect the sensory ganglia following heterotypic genital HSV challenge. In Aim 3, we will analyze the protective role of CD4+ T cells in neuronal tissue. We will use cell depletion and adoptive transfer experiments to test the dependence of the HSV-specific recall antibody response and neuronal CD8+ T cell response on CD4+ T cells. Additionally, we will utilize adoptive transfer of immune CD4+ T cells to immunodeficient mice to determine if CD4+ T cells contribute to HSV clearance from neuronal tissue. The results of these studies should be important for the rational development of HSV vaccines as well as understanding the cellular interactions and specific molecular mechanisms required for resolution of HSV lesions.